IPAC2012 - List of Authors (Sammut, N.J.)

Paper	Title	Page
MOPPD079	Preliminary Thermo-Mechanical Analysis of Angular Beam Impact on LHC Collimators	550
	M. Cauchi, R.W. Assmann, A. Bertarelli, F. Carra, A. Dallocchio, D. Deboy, N. Mariani, A. Rossi CERN, Geneva, Switzerland L. Lari IFIC, Valencia, Spain P. Mollicone UoM, Msida, Malta N.J. Sammut University of Malta, Faculty of Engineering, Msida, Malta
	Funding: This work is supported by EuCARD. The correct functioning of the LHC collimation system is crucial to attain the desired LHC luminosity performance. However, the requirements to handle high intensity beams can be demanding. In this respect, accident scenarios must be well studied in order to assess if the collimator design is robust against likely error scenarios. One of the catastrophic - though not very probable - accident scenarios identified is an asynchronous beam dump coupled with slight angular misalignment errors of the collimator jaw. Previous work presented a preliminary thermal evaluation of the extent of beam-induced damage for such scenarios, where it was shown that in some cases, a tilt of the jaw could actually serve to mitigate the effect of an asynchronous dump on the collimators. This paper will further analyze the response of tertiary collimators in presence of such angular jaw alignments, with the aim to identify optimal operational conditions.

TUPPR097	Modeling and Simulation of LHC Beam-Based Collimator Setup	2059
	G. Valentino, N.J. Sammut University of Malta, Information and Communication Technology, Msida, Malta R.W. Assmann, F. Burkart, S. Redaelli, A. Rossi, D. Wollmann CERN, Geneva, Switzerland L. Lari IFIC, Valencia, Spain
	In the 2011 Large Hadron Collider run, collimators were aligned for proton and heavy ion beams using a semi-automatic setup algorithm. The algorithm provided a reduction in the beam time required for setup, an elimination of beam dumps during setup and higher accuracy with respect to manual alignment. A collimator setup simulator was developed based on a Gaussian model of the beam distribution as well as a parametric model of the beam losses. A time-varying beam loss signal can be simulated for a given collimator movement into the beam. The simulation results and comparison to measurement data obtained during collimator setups and dedicated fills for beam halo scraping are presented. The simulator will then be used to develop a fully automatic collimator alignment algorithm.

TUPPR098	Comparison of LHC Collimator Beam-Based Alignment Centers to BPM-Interpolated Centers	2062
	G. Valentino, N.J. Sammut University of Malta, Information and Communication Technology, Msida, Malta R.W. Assmann, R. Bruce, G.J. Müller, S. Redaelli, A. Rossi, G. Valentino CERN, Geneva, Switzerland L. Lari IFIC, Valencia, Spain
	The beam centers at the Large Hadron Collider collimators are determined by beam-based alignment, where both jaws of a collimator are moved in separately until a loss spike is detected on a Beam Loss Monitor downstream. Orbit drifts of more than a few hundred micrometers cannot be tolerated, as they would reduce the efficiency of the collimation system. Beam Position Monitors (BPMs) are installed at various locations around the LHC ring, and a linear interpolation of the orbit can be obtained at the collimator positions. In this paper, the results obtained from beam-based alignment are compared with the orbit interpolated from the BPM data throughout the 2011 LHC proton run. The stability of the orbit determined by collimator alignment during the run is evaluated.

WEEPPB014	The Magnetic Model of the LHC during the 3.5 TeV Run	2194
	E. Todesco, N. Aquilina, M. Giovannozzi, M. Lamont, F. Schmidt, R.J. Steinhagen, M. Strzelczyk, R. Tomás CERN, Geneva, Switzerland N.J. Sammut University of Malta, Information and Communication Technology, Msida, Malta
	The magnetic model of the LHC is based on a fit of the magnetic measurements through equations that model the field components (geometric, saturation, persistent) at different currents. In this paper we will review the main results related to the magnetic model during the run of the LHC in 2010-2011: with a top energy of 3.5 TeV, all components of the model but the saturation are visible. We first give an estimate of the reproducibility of the main components and multipolar errors as they can be deduced from beam measurements, i.e. orbit, tune, chromaticity, beta beating and coupling. We then review the main results relative to the decay at injection plateau, dependence on powering history, and snapback at the beginning of the ramp for both tune and chromaticity. We discuss the precision obtained in tracking the magnets during the ramp, where the persistent current components gradually disappear. We conclude by presenting the behaviour of the quadrupoles model during the squeeze. A list of the major changes implemented during the operation together with what are considered as the main open issues is given.

Paper

Title

Page

Preliminary Thermo-Mechanical Analysis of Angular Beam Impact on LHC Collimators

550

M. Cauchi, R.W. Assmann, A. Bertarelli, F. Carra, A. Dallocchio, D. Deboy, N. Mariani, A. Rossi
CERN, Geneva, Switzerland
L. Lari
IFIC, Valencia, Spain
P. Mollicone
UoM, Msida, Malta
N.J. Sammut
University of Malta, Faculty of Engineering, Msida, Malta

Funding: This work is supported by EuCARD.
The correct functioning of the LHC collimation system is crucial to attain the desired LHC luminosity performance. However, the requirements to handle high intensity beams can be demanding. In this respect, accident scenarios must be well studied in order to assess if the collimator design is robust against likely error scenarios. One of the catastrophic - though not very probable - accident scenarios identified is an asynchronous beam dump coupled with slight angular misalignment errors of the collimator jaw. Previous work presented a preliminary thermal evaluation of the extent of beam-induced damage for such scenarios, where it was shown that in some cases, a tilt of the jaw could actually serve to mitigate the effect of an asynchronous dump on the collimators. This paper will further analyze the response of tertiary collimators in presence of such angular jaw alignments, with the aim to identify optimal operational conditions.

TUPPR097

Modeling and Simulation of LHC Beam-Based Collimator Setup

2059

G. Valentino, N.J. Sammut
University of Malta, Information and Communication Technology, Msida, Malta
R.W. Assmann, F. Burkart, S. Redaelli, A. Rossi, D. Wollmann
CERN, Geneva, Switzerland
L. Lari
IFIC, Valencia, Spain

In the 2011 Large Hadron Collider run, collimators were aligned for proton and heavy ion beams using a semi-automatic setup algorithm. The algorithm provided a reduction in the beam time required for setup, an elimination of beam dumps during setup and higher accuracy with respect to manual alignment. A collimator setup simulator was developed based on a Gaussian model of the beam distribution as well as a parametric model of the beam losses. A time-varying beam loss signal can be simulated for a given collimator movement into the beam. The simulation results and comparison to measurement data obtained during collimator setups and dedicated fills for beam halo scraping are presented. The simulator will then be used to develop a fully automatic collimator alignment algorithm.

TUPPR098

Comparison of LHC Collimator Beam-Based Alignment Centers to BPM-Interpolated Centers

2062

G. Valentino, N.J. Sammut
University of Malta, Information and Communication Technology, Msida, Malta
R.W. Assmann, R. Bruce, G.J. Müller, S. Redaelli, A. Rossi, G. Valentino
CERN, Geneva, Switzerland
L. Lari
IFIC, Valencia, Spain

The beam centers at the Large Hadron Collider collimators are determined by beam-based alignment, where both jaws of a collimator are moved in separately until a loss spike is detected on a Beam Loss Monitor downstream. Orbit drifts of more than a few hundred micrometers cannot be tolerated, as they would reduce the efficiency of the collimation system. Beam Position Monitors (BPMs) are installed at various locations around the LHC ring, and a linear interpolation of the orbit can be obtained at the collimator positions. In this paper, the results obtained from beam-based alignment are compared with the orbit interpolated from the BPM data throughout the 2011 LHC proton run. The stability of the orbit determined by collimator alignment during the run is evaluated.

WEEPPB014

The Magnetic Model of the LHC during the 3.5 TeV Run

2194

E. Todesco, N. Aquilina, M. Giovannozzi, M. Lamont, F. Schmidt, R.J. Steinhagen, M. Strzelczyk, R. Tomás
CERN, Geneva, Switzerland
N.J. Sammut
University of Malta, Information and Communication Technology, Msida, Malta

The magnetic model of the LHC is based on a fit of the magnetic measurements through equations that model the field components (geometric, saturation, persistent) at different currents. In this paper we will review the main results related to the magnetic model during the run of the LHC in 2010-2011: with a top energy of 3.5 TeV, all components of the model but the saturation are visible. We first give an estimate of the reproducibility of the main components and multipolar errors as they can be deduced from beam measurements, i.e. orbit, tune, chromaticity, beta beating and coupling. We then review the main results relative to the decay at injection plateau, dependence on powering history, and snapback at the beginning of the ramp for both tune and chromaticity. We discuss the precision obtained in tracking the magnets during the ramp, where the persistent current components gradually disappear. We conclude by presenting the behaviour of the quadrupoles model during the squeeze. A list of the major changes implemented during the operation together with what are considered as the main open issues is given.